Container number check digit
ISO 6346 calculator and validator — enter 10 characters to compute the check digit, or 11 to verify the full number. Input is uppercased and stripped to A–Z/0–9 as you type; nothing is sent to the server.
10 characters calculates the check digit; 11 validates the full number.
About ISO 6346
Every freight container carries an 11-character container number — three-letter owner code, equipment category (U freight, J detachable, Z chassis/trailer), six-digit serial, and a modulo-11 check digit.
Depot systems and documentation platforms validate the check digit before accepting a record. ConPDS Checker and Tracker run the same check at capture; this page is for manual verification or completing a partial read.
Worked example: CSQU305438 → check digit 3 → CSQU3054383
Entering container numbers manually is where filing errors start. ConPDS Checker validates at capture.